Programming and Read-back Processes on Phase-Change Materials during Surface Scanning.

Scanning probe methods, based on micro-electromechanical (MEMS) devices, have been employed to store data at ultrahigh densities (>Tbit/sq.in) with low power consumption. The use of microscopic conductive tip in contact with phase-change materials (PCM) is one such approach, with the aim to record data as amorphous or crystalline marks on a sample medium down to the nanometer scale. These applications rely on the reversible phase transition property of PCM between amorphous and (poly)crystalline state. Writing data is a complex process which involves electrical, thermal and phase-transition phenomena that determine the final size and shape of the written mark. Reading is based on the detection of the large difference between electrical conductivities of the two states of the phase-change medium. Towards a better understanding of these processes, numerical models, based on finite element methods (FEM), have been developed to simulate and analyze such a system. The objective of this paper is to present a theoretical study based on computational calculations, in order to predict the spatial distribution of amorphization during writing and derive the basic waveform of the read-back signal. [ABSTRACT FROM AUTHOR]